This invention relates to the field of radiant or optical energy sources of the type providing output in the visible, near infrared, and far infrared spectral regions.
For testing the ability of a guidance system such as might be employed in a present-day missile weapon of the infrared responsive type, it is desirable to employ optical energy sources capable of providing controllable bursts of radiant energy of predetermined spectral content for simulated target energizing of the missile guidance system. The energy sources used for this purpose should desirably have multi-wavelength high irradiance capability and small physical size. Such characteristics enable the testing of a variety of guidance system sensors having differing spectral frequency responses and allows airborne use of the energy source for in-flight guidance system testing. For such airborne guidance system testing, a plurality of energy sources might, for example, be mounted around the periphery of a drone or piloted aircraft so as to be visible over a wide azimuth. Energy source use in airborne environments, of course, emphasizes the need for small size, minimum weight, and rugged vibration-immune construction. The airborne environment also involves the presence of a large range of environmental conditions including high humidity, high temperature ground level conditions and sub-zero low humidity, high altitude flight level conditions--conditions that are together capable of taxing the endurance of conventional energy sources.
In order that such a simulated-target energy source be capable of replicating the on-off defensive and operating characteristics of in real-life infrared signature targets, it is desirable to include therein an energy modulation capability for terminating the irradiated energy either periodically or in response to a command signal. Since the electrical energy transducer devices, such as resistance heaters or lamps, that are desirable for use as sources of infrared energy, inherently require a relatively long period of warm-up to achieve stable spectral and amplitude outputs, it is additionally desirable for a simulated target source of this type to use modulation other than interruption of electrical energy supply. Mechanical shuttering in the form of energy path blocking devices or physically relocatable mirror arrangements have been found particularly suitable for providing such modulation of simulated target energy.
Energy sources of this same general capability are also useful in signalling devices, weapon deception equipment, and in other military apparatus, both in airborne and ground environments, as well as for shipboard and nautical equipment. For such alternate uses, portions of the energy spectrum in addition to the preferred far infrared region applicable to infrared missile acquisition and tracking systems, i.e., visible spectrum and near infrared spectrum energy, may also be attractive.
The patent art includes a number of lamps, lamp housing arrangements and optical systems usable for providing visible and infrared spectrum optical energy output. Included in this art is the patent of Kiyoshi Suzuki, U.S. Pat. No. 4,343,033, which concerns a marker light for use in an airport and similar environments wherein an apparatus is to be embedded in the earth and is to comprise a part of some structure such as a runway. The Suzuki light includes a source of visible spectrum energy and a plurality of optical elements including lenses, reflectors, and environmental sealing members.
Another lamp fixture suitable for use in aircraft runways and similar environments is shown in the patent of R. W. Cumming, U.S. Pat. No. 2,934,633, which describes a ruggedized earth-mountable structure capable of providing visible spectrum emission.
Other examples of optical energy source apparatus are found in the patents of E. L. Hopkins et al, U.S. Pat. No. 3,532,433, an automotive headlamp aiming system; J. R. Townsend, U.S. Pat. No. 1,628,862, a locomotive headlamp; Richard J. Heimer, U.S. Pat. No. 4,241,389, a multiple source imaging system; A. S. Limpert, U.S. Pat. No. 1,421,506, an automotive headlamp; D. J. Bulic, U.S. Pat. No. 3,219,809, a glareless automotive headlamp; and William A. Castic, U.S. Pat. No. 3,919,542, a floodlight frame assembly.
These patent art energy sources fall short of providing a shutter-modulated source of well diffused radiant energy capable of extending into the far infrared region and capable of use in the widely varying and hostile environment of an aircraft or other military applications.